A patch antenna is a known in-vehicle antenna device that can be used for a non-stop automatic toll collection system (ETC: Electronic Toll Collection System). The patch antenna is referred to as a microstrip antenna and has a short height and a narrow bandwidth. The patch antenna has a structure in which an antenna element thereof is provided on a ground conductor with a substrate or an air gap positioned in between.
Further, there is an antenna device that incorporates an electric circuit such as a light-emitting diode, a speaker, or the like so as to exhibit a function of reporting the operation or state of the antenna device, like one disclosed in Patent Document 1 or Patent Document 2. A microstrip antenna with a light-emitting diode disclosed in Patent Document 1 has a light emitting diode provided at a part where the potential difference between an antenna element and a ground conductor becomes minimal when the antenna element resonates to thereby reduce the area of a substrate around the periphery of the antenna element. A speaker-integrated antenna disclosed in Patent Document 2 has a configuration in which a piezoelectric ceramic member is stuck on a ground conductor so as to provide a speaker function to the ground conductor and for reducing the antenna device size. A speaker circuit is connected to the feeding point of the antenna element.    Patent Document 1:    Japanese Patent Application Kokai Publication No. 2006-166041    Patent Document 2:    Japanese Patent Application Kokai Publication No. 2006-186881